French investigators say the co-pilot who deliberately brought down a Germanwings airliner in the French Alps in March, killing 150 people, apparently practiced such a controlled descent during an earlier flight the same day.

The settings for "selected altitude" on the autopilot were adjusted several times - and set as low as 30 meters - as the plane descended on the first leg into Barcelona, notes a report issued Wednesday by the BEA (Bureau d'Enquêtes et d'Analyses), the French authority responsible for safety investigations into accidents or incidents in civil aviation.

In a 30-page report, the investigators say co-pilot Andreas Lubitz was alone in the cockpit during the initial descent, as he was when the Germanwings flight made its fatal descent hours later during the return to Dusseldorf, Germany.

The revelation that Lubitz may have rehearsed the maneuver appears to support the assumption the crash was not only deliberate but also premeditated.

Earlier findings indicated Lubitz locked the pilot out of the cockpit when the pilot went to the lavatory an hour after the flight left Barcelona for Dusseldorf.

They say Lubitz then put the Airbus A320 into a steady descent, ignoring the pilot's frantic demands to open the cockpit door - demands which could be heard on the plane's cockpit voice recorder.

Late last month, mourners gathered at Germany's Cologne Cathedral for a memorial service honoring the victims of the crash.

German Chancellor Angela Merkel, German President Joachim Gauck, and officials from France and Spain attended the service, as well as Germanwings and Lufthansa officials.

Lufthansa is the parent company of Germanwings, which is a short-distance passenger airline.